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f0d8edecee
Fixed: tint:1813 Change-Id: I97b7c0c0a4bfdda2f7e63983caddcfb3a1e19c2f Reviewed-on: https://dawn-review.googlesource.com/c/dawn/+/117215 Reviewed-by: dan sinclair <dsinclair@google.com> Kokoro: Ben Clayton <bclayton@google.com> Auto-Submit: Ben Clayton <bclayton@google.com> Commit-Queue: Ben Clayton <bclayton@google.com>
103 lines
3.5 KiB
C++
103 lines
3.5 KiB
C++
// Copyright 2021 The Tint Authors.
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//
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// Licensed under the Apache License, Version 2.0 (the "License");
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// you may not use this file except in compliance with the License.
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// You may obtain a copy of the License at
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//
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// http://www.apache.org/licenses/LICENSE-2.0
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//
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// Unless required by applicable law or agreed to in writing, software
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// distributed under the License is distributed on an "AS IS" BASIS,
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// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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// See the License for the specific language governing permissions and
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// limitations under the License.
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#ifndef SRC_TINT_UTILS_MATH_H_
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#define SRC_TINT_UTILS_MATH_H_
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#include <sstream>
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#include <string>
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#include <type_traits>
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namespace tint::utils {
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/// @param alignment the next multiple to round `value` to
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/// @param value the value to round to the next multiple of `alignment`
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/// @return `value` rounded to the next multiple of `alignment`
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/// @note `alignment` must be positive. An alignment of zero will cause a DBZ.
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template <typename T>
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inline constexpr T RoundUp(T alignment, T value) {
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return ((value + alignment - 1) / alignment) * alignment;
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}
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/// @param value the value to check whether it is a power-of-two
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/// @returns true if `value` is a power-of-two
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/// @note `value` must be positive if `T` is signed
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template <typename T>
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inline constexpr bool IsPowerOfTwo(T value) {
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return (value & (value - 1)) == 0;
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}
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/// @param value the input value
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/// @returns the base-2 logarithm of @p value
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inline constexpr uint32_t Log2(uint64_t value) {
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#if defined(__clang__) || defined(__GNUC__)
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return 63 - static_cast<uint32_t>(__builtin_clzll(value));
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#elif defined(_MSC_VER) && !defined(__clang__) && __cplusplus >= 202002L // MSVC and C++20+
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// note: std::is_constant_evaluated() added in C++20
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// required here as _BitScanReverse64 is not constexpr
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if constexpr (!std::is_constant_evaluated()) {
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// NOLINTNEXTLINE(runtime/int)
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if constexpr (sizeof(unsigned long) == 8) { // 64-bit
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// NOLINTNEXTLINE(runtime/int)
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unsigned long first_bit_index = 0;
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_BitScanReverse64(&first_bit_index, value);
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return first_bit_index;
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} else { // 32-bit
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// NOLINTNEXTLINE(runtime/int)
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unsigned long first_bit_index = 0;
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if (_BitScanReverse(&first_bit_index, value >> 32)) {
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return first_bit_index + 32;
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}
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_BitScanReverse(&first_bit_index, value & 0xffffffff);
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return first_bit_index;
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}
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}
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#endif
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// Non intrinsic (slow) path. Supports constexpr evaluation.
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for (uint64_t clz = 0; clz < 64; clz++) {
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uint64_t bit = 63 - clz;
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if (value & (static_cast<uint64_t>(1u) << bit)) {
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return static_cast<uint32_t>(bit);
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}
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}
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return 64;
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}
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/// @param value the input value
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/// @returns the next power of two number greater or equal to @p value
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inline constexpr uint64_t NextPowerOfTwo(uint64_t value) {
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if (value <= 1) {
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return 1;
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} else {
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return static_cast<uint64_t>(1) << (Log2(value - 1) + 1);
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}
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}
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/// @param value the input value
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/// @returns the largest power of two that `value` is a multiple of
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template <typename T>
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inline std::enable_if_t<std::is_unsigned<T>::value, T> MaxAlignOf(T value) {
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T pot = 1;
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while (value && ((value & 1u) == 0)) {
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pot <<= 1;
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value >>= 1;
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}
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return pot;
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}
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} // namespace tint::utils
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#endif // SRC_TINT_UTILS_MATH_H_
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